There has always been a need for processing various materials to reduce particle size. For example, grains and forage materials are routinely ground or cut into small particles prior to feeding such materials to animals or otherwise using or processing such materials. Numerous other materials in a wide variety of industries are also routinely chopped, cut, ground, or otherwise reduced in particle size before being further processed or used.
For example, in addition to the grains and forage materials described above, other materials which must be reduced in particle size include waste wood, paper, waste products (such as spoiled food, e.g., fruits and vegetables), plant and animal waste products, compost, metal, glass, etc. Other recyclable products and materials are also reduced in particle size before they can be effectively used.
Conventional devices which are routinely used for grinding or reducing particle size of materials typically include a rotating wheel having hammers on the periphery thereof. A curved screen is positioned in close proximity to the path of the rotating hammers. The screen typically covers only a small portion of the circumference of the rotating wheel with hammers. The remainder of the grinding chamber is closed to prevent escape of the material being ground.
The material being reduced in particle size is repeatedly hammered by the rotating hammers until it is able to pass through the openings in the screen. For example, this is the operation of a conventional hammer mill which is used to grind grain and other such materials.
Such types of hammer mills are described, for example, in U.S. Pat. No. 4,325,516; German Patent 3324467A; and U.S.S.R. documents 1087114A and 910189.
Another variation of hammer mill is a so-called tub grinder in which the material to be ground is placed in a very large tub (several feet in diameter). The tub has an opening in the floor in which the outer portion of a rotating wheel is positioned. On the periphery of the wheel there are fastened a number of hammers. A screen is positioned below the floor of the tub and in close proximity to the ends of the hammers as the wheel is rotated. The screen covers a small portion of the circumference of the rotating wheel. When the wheel is rotated at high speed the hammers pound on the material in the tub until the material is able to pass through the openings in the screen. The tub also rotates so as to urge the material into the path of the rotating hammers on the wheel. A variation of this type of tub grinder is described in U.S. Pat. No. 4,142,686.
There are numerous disadvantages associated with both the hammer mill machines and the tub grinders. For example, both types of machines are limited in capacity because the material must pass through small openings in a screen in order to escape the grinding chamber. The screen only covers a portion of the circumference of the rotating wheel. Furthermore, in both types of machines the material being processed is fed only to a very small fraction of the circumference of the rotating wheel. Therefore, there is a small feed area and a small grinding area presented.
Another disadvantage of the tub grinder is that a large amount of horsepower is required for the volume of material processed. Another disadvantage of the tub grinder is that it has a large number of moving parts which are subject to a great amount of wear. Furthermore, the tub grinder is limited in capacity in spite of the large size of the machine. Still another disadvantage of the tub grinder is that it can throw material into the air well above the top of the tub. This presents a very dangerous situation, for example, when there are rocks or other heavy objects present in the material being ground.
Although roller mills have been used to process small grains, such devices are not useful for reducing particle size of various other materials. Forage grinders utilizing a large reel with knives at the edge have also been used for chopping forage materials; but such devices are not useful for grains or other products of small particle size.
Various other structures are described in the patents and documents listed below. None of such structures is suitable for the purposes of the present invention:
U.S. Pat. Nos. 2,997,968 4,227,654 3,197,084 French Patent 1,120,386 U.S. Pat. No. 3,208,167 French Patent 7,425,289 U.S. Pat. No. 3,675,856 Germany Patent 1,224,552 U.S. Pat. No. 3,749,321 Germany Patent 230,798 U.S. Pat. No. 3,782,642 Switzerland 366,415 U.S. Pat. No. 4,469,210 U.S.S.R. 882,444
Pulverizing devices have been described in U.S. Pat. Nos. 4,214,716 and 3,214,105. Such devices include an upright rotor supported at upper and lower ends and including a plurality of hammers. One of the devices includes stationary striker blades. Such devices do not include a cavity below the rotor to receive processed material, nor do such devices have the capability to process bales of bulk material, among other things. They also have other operating limitations and disadvantages.
There has not heretofore been described a material processor for reducing particle size having the advantages provided by the apparatus of the present invention.